High and low speed leveling control for an elevator with tach speed sensor



March 15, 1966 R. B. POHLMAN 3,240,290

HIGH AND LOW SPEED LEVELING CONTROL FOR AN ELEVATOR WITH TACH SPEED SENSOR Filed Aug. 25, 1962 4 Sheets-Sheet 1 /0 MG. SET

ELEVATOR DIRECTION, BRAKE 8: SLOWDOWN /Z 02 GENERATOR j I 4 3 SHUNT FIELD U2 SPEED P2 \/\/\/V\/"'| CONTROLLER fl TAcHoM TER LEFi R1 R2 H515 II I L T IV 61 l r" LRF2 C2 d.

P3 LUi LD1 u [I] {I} KPAX \J F/Gf INVENTOR RAYMOND B. POHLMAN BYW E'W his ATTORNEYS March 15, 966 R. B. POHLMAN 3,240,290

HIGH AND LOW SPEED LEVELING CONTROL FOR AN ELEVATOR WITH TACH SPEED SENSOR 4 Sheets-Sheet 2 Filed Aug. 25, 1962 115 V.A.C.

ILEVELING UNITS ,LOW LEVELER 12 V.A.C.

LEF2

ELEVATOR DRIVE MEANS INVENTOR. RAYMOND B. POHLMAN blue 12 m $9M- his ATTORNEYS March 15, 1966 R. B. POHLMAN 3,240,290

HIGH AND LOW SPEED LEVELING CONTROL FOR AN ELEVATOR WITH TACH SPEED SENSOR Filed Aug. 25, 1962 4 Sheets-Sheet 5 D LD LEF LRF LU P PA U V in) g E-PAHZ) -Pun um) 1 95pm) EEuzm DH1) LEF1(1) ELEFZ Tum-1m LRF2(1) ELDH Elm =P3 in) INVENTOR.

RAYMOND B. POHLMAN BY 6., uwfiwam PMM his ATTORNEYS March 15, 1966 PQHLMAN 3,240,290

HIGH AND LOW SPEED LEVELING CONTROL FOR AN ELEVATOR WITH TACH SPEED SENSOR Filed Aug. 23, 1962 4 Sheets-Sheet 4 A? SPEED CONTROLLER W VARIABLE COMPENSATION CONTROL Z3 54 M (FIG.I.) COMPENSATION CONTROL (FIG. 2.)

FIG. 4.

INVENTOR.

RAYMON D B. POH LMAN ATTORNEYS.

United States Patent HIGH AND LOW SPEED LEVELING CONTROL FOR AN ELEVATOR WITH TACH SPEED SENSOR Raymond B. Pohlman, Memphis, Tenn., assignor to Dover Corporation, Memphis, Tenn., a corporation of Delaware Filed Aug. 13, 1962, Ser. No. 216,470 3 Claims. (Cl. 18729) The present invention relates to an elevator control system and, more particularly, to novel and improved apparatus for controlling the leveling of an elevator car at a floor at which it is being stopped.

The accurate control of leveling and stopping of elevator cars has long been a subject of much development and innovation in the elevator industry. In particular, in the field of high speed passenger elevator installations, the ability to accurately level a car at a floor in a smooth stopping action has been a matter not Only of practical necessity, but of important commercial advantage in a highly competitive field. In order to achieve a consistently accurate stop at a floor the final approach speed must be kept stable and the final stopping action must be as slow as possible for the comfort of the passengers. Thus control of the final few inches of travel of the elevator car becomes exceedingly important. If a low stable speed is obtained during this final approach, the accuracy of leveling can be greatly increased.

The Ward Leonard type of motor-generator control system is widely used as the drive means for traction elevators. A motor-generator system of this type has a serious drawback in that control is limited in the lowest operating speeds by the residual voltage present in the generator when the field excitation of the generator is reduced to zero. In most cases, the residual 'voltage is in an order of magnitude of approximately of the full voltage output of the generator. In order to have a stable system, the shunt field excitation must be kept at a value slightly higher than the residual voltage which is susceptible of variation as a function of the length of run, the rate of deceleration, and other well known factors.

In a high speed elevator installation, this residual voltage results in a speed of travel in the final approach to a floor that is equal to $4 of the normal high speed of the elevator car. Such a speed is not consonant with a smooth and accurate stopping action. In order to overcome the effects of this residual voltage, it has been necessary to provide a strong retarding action by the braking means. However, the varying coeificient of friction caused by heating and humidity prevents the consistent production of an accurate stop irrespective of the strength of the braking action.

In accordance with the invention, these and other disadvantages of the conventional form of leveling control in traction elevator systems may be overcome by the utilization of a compensating means which is responsive to the speed of travel of the elevator car and operative when the elevator car is leveling at a floor for modifying the control of the drive means, for example, through the provision of a feedback compensating winding on the electrical generator of the motor generator set for the elevator car which is energized by an electrical output signal responsive to the speed and direction of travel of the elevator car during leveling.

For a more complete understanding of the invention reference may be had to the following detailed description taken in conjunction with the accompanying figures of the drawings, in which:

FIGURES 1 and 2 are electrical schematic diagrams of an exemplary embodiment of an electrical control system, in accordance with the invention;

ice

FIG. 3 is a straight-line diagram corresponding respec tively to FIGS. 1 and 2, and showing the relative location of relays and their respective contacts; and

FIG. 4 is a schematic diagram depicting in a single figure the functional operating controls of the system of FIGS. 1 and 2.

As an aid in understanding the invention as illustrated in the exemplary embodiment of the drawings, each of the various contacts associated with particular relays bear the same letter designation as the respective relays plus the distinguishing numerical suffix. Further, the condition of the contact as shown in the drawings, i.e. open or closed, is the condition of the contact with its controlling relay deenergized.

The relays disclosed in the exemplary embodiment of the drawing bear the following functional designations:

DDown direction relay LDDown high speed leveling relay LEF-Leveling feedback relay LRFLow speed leveling feedback relay LUUp high speed leveling relay P-Potential relay PA-Running relay UUp direction relay VSlow down relay Only those portions of the elevator control system directly involved in the operation and functioning of the compensating system of the invention are illustrated in the drawings or described in detail hereinafter, in order to clearly indicate the nature of the specific improvement in an elevator control system to which the invention appertains and to particularly point out such parts as necessarily cooperate with the subject matter of the invention and may be necessary for a complete understanding of the invention by persons skilled in the elevator art.

In FIGS. 1 and 4, a conventional controllable electrical drive means 10 have a controllable electrical generating means 11 is used to raise and lower an elevator car between a plurality of floors. The controllable electrical drive means 10 may operate as a Ward Leonard motorgenerator control system at selectively variable speeds, in accordance with operating principles and techniques long known in the elevator art. The motor controlled by the electrical generating means 11, the customary sheaves, cabling and mechanical connections as well as the elevator cars, are not shown, as they do not form any part of the invention and may be of any typical construction.

A shunt field winding 12 for the electrical generating means 11 is selectively energized across the electrical busses 101 and 102, which are preferably energized from a source of unidirectional current, in accordance with the intended direction of travel of the elevator car when the elevator car is to be operated. A speed controller 13, which may take any suitable conventional formand incorporate any and all necessary circuitry is connected at least in part in series relation with the generator shunt field 12 between the busses 10 1 and 102. The direction, brake and slow down controls are generally represented by rectangle 14 and are intended to include and incorporate therein any and all necessary circuits for the control of the enumerated functions, such as are well known in the elevator art. For the purpose of a clear understanding of the present invention, the controls 14 include a conventional relay P, which is energized whenever electrical potential is supplied to the elevator drive means and the brake is energized; a relay V, which is energized when the conventional hall or car call pickup circuits initiate the slow down of the elevator car; and up and down direction relays U and D, which are respectively energized in accordance with the intended direction of travel of the elevator car.

When the elevator car is to be raised or lowered between floors, the potential relay P is energized and closes the normally open contacts P1 and P2, enabling the energization of the generator shunt field 12 and the speed controller 13, which energization is complete when either the up or down direction relays U or D are energized to alternatively close their respective contacts U1 and U2 or D1 and D2. It is to be assumed that the elevator car is now running between floors in accordance with conventional elevator control techniques. The running condition of the car is indicated by the energization of the running relay PA across the busses 101 and 102 through a now closed contact P3 and the normally closed contacts LU1 and LD1, which remain in their normally closed condition except during the leveling of the car at a stop.

The electrical output signal producing means (FIG. 2) includes a conventional tachometer generator armature 16, which is driven through a suitable mechanical coupling 17 from the elevator drive means generally shown at 18. The tachometer generator may be driven by the selector of a geared machine, or the brake pulley of a .gearless machine, for example. When the elevator car is running between the floors, there is no output from the electrical output signal producing means 15, since the tachometer generator field 19 (FIG. 1) is deenergized by the normally open contact LEFl of the leveling feedback relay LEF.

As the elevator car aproaches a floor at which it is to stop in response to the registration of a hall or car call, for example, the conventional call pickup circuits (not shown) initiate the energization of the slow down relay V (FIG. 1), which in turn closes the normally open Contact VI (FIG. 2) in the energizing circuits for the up and downhigh speed leveling relays LU and LD. As the car comes into the high speeed leveling zone and assuming that it is traveling in the up directipn, leveling contact 21 closes, thereby completing the energization of the up high speed leveling relay LU. Leveling contact 21 and the leveling contact 22, closed when the car is in the high speed leveling zone approaching a floor in the down direction, may be controlled by any conventional form of leveling circuitry, the details of which do not form a part of the present invention. The energization of the up high speed leveling relay LU opens a normally closed contact LU1 in the energizing circuit for the running relay PA, deenergizing the PA relay and restoring the contact PA I in the energizing circuit for the leveling feedback relay LEF to its normally closed condition to energize the LEF relay. Energization of the LEF relay results in the closing of normally open contact LEFI in the energizing circuit for the tachometer generator field 19, which is energized from the busses 101 and 102 through two variable resistances R1 and R2. A normally open contact LEFZ (FIG. 2) is also closed placing a rectifying means 23, which may take any suitable conventional form, but in this case is shown as a full wave recifier, across a twelve volt alternating current supply fed through a transformer 24 from a pair of alternating current supply busses 201 and 202, thus providing a low voltage unidirectional current output across conductors 25 and 26.

Under normal conditions, with the tachometer generator field 19 energized and the tachometer generator .armature 16 being driven in response to the operation of the elevator drive means 18, a voltage drop is produced in the electrical output signal producing means 15 across a pair of load resistances 2-8 and 29 to provide two electrical output signals between the variable taps of the resistances 28 and 29 and a common point between the resistances. The electrical output signal produced between the tap of resistance 28 and the common point 30 is fed to an electrical transducing means 31, and the electrical output signal produced between the tap of the resistance 29 and the common point 30 is fed to an electrical transducing means 32 in push-pull relation to transducer means 31 with respect to a pair of compensating field windings 33 and 34 for the electrical generating means 11.

The common point 35 between electrical transducing means 31 and 32 is connected to the common point 30 of the electrical output signal producing means 15 and the output conductor 25 of the rectifying means 23. A common point 36 between the compensating field windings 33 and 34 is connected to the other output conductor 26 of the rectifying means 23. The electrical transducing means 3 1 and 32 are shown as transistors with their respective bases B connected to the variable taps of the resistances 28 and 29. The collectors C of the transducer means 31 and 32 are connected respectively to the compensating field windings 33 and 34. The emitters E of the transducer means 31 and 32 are connected to the common point 3 5.

The tachometer generator armature 16 of the electrical output signal producing means 15 is rotated in a direction dependent upon the direction of travel of the elevator car by virtue of the mechanical linkage 17 to the elevator drive means 18. Therefore, the polarity of the output signals appearing on the taps of the resistances 28 and 29 relative to the common point 30 vary as a function of the direction of travel of the elevator car. Since the inputs to the electrical transducing means 3 1 and 32 are responsive to these output signals, conduction by the electrical transducer means 31 and 32 and, therefore, the energization of compensating field windings 33 and 34 are selectively controlled as a function of the direction of travel of the elevator car.

The speed of rotation of the tachometer generator armature 16 varies as a function of the speed of travel of the elevator car so that the magnitude of the electrical signal outputs fed from the variable taps of the resistances 28 and 29 to the electrical transducing means 31 and 32 varies as a function of the speed of the elevator car. Thus one or the other of the compensating field windings 33 and 34 is selectively energized as a function of the direction and speed of travel of the elevator car. The energization of one or the other of the compensating field windings 33 and 34 modifies the control of the electrical generating means on the travel of the elevator car to provide a compensating feedback. It is intended that the flux produced by the selected compensating field is of opposite polarity to the flux of the main generator shunt field 12.

As the elevator car slows down and comes into the low speed leveling zone a contact 38, controlled in any conventional manner by a circuit means not forming part of the invention, is closed in the energizing circuit of a low speed leveling feedback relay LRF (FIG. 2) to energize the LRF relay through the normally closed PA1 contact. The LRF relay in turn closes a normally open contact LRFll shunting the resistance R1 in series with the tachometer generator field 19. During high speed slow down, a capacitance C1 is connected in parallel with the tachometer generator field 19. During low speed leveling, a normally open contact LRF2 is closed by means of relay LRF to place a capacitance C2 in parallel with the capacitance 01.

In operation, the generator shunt field winding 12 is initially set and adjusted so that the car approaches the floor at which it is to stop at a stable speed. The electrical output signal producing means 15 produces a constant output voltage which is fed through one of the electrical transducing means 31 and 32, depending upon the direction of travel of the elevator car, to energize the respective compensating field windings 33 or 34. The flux produced by the selected compensating field winding is of an opposite polarity to the flux of the generator shunt field winding 12, so that the total effective shunt field is less than that produced by the shunt field winding .12. Thus the electrical generating means 11 produces a lower output voltage resulting in a lower elevator speed.

If for any reason, the car is approaching the floor at a speed greater than the selected value, the speed of the tachometer generator armature 16 will be greater than its normally expected value resulting in the production of a higher output voltage signal fed into the selected compensating field winding. Thus the effective shunt field flux is reduced and the car speed is reduced to the normal selected value. If the elevator car is approaching a floor at a speed less than the selected value, the speed of the tachometer generator armature 16 is reduced and the output signal from the electrical output signal producing means 15 to the selected compensating field winding 33 or 34 is reduced, resulting in an increase in the effective shunt field of the electrical generating means 11 and an increase in car speed to the normal selected value.

Since the resistance of the tachometer generator armature 16 is normally much greater than the resistance of the compensating field windings 33 and 34, it is necessary to match the effective impedances to obtain a maximum power transfer from the electrical output signal producing means to the compensating field windings. The variable resistances 28 and 29 constitute an impedance matching means to perform this function.

The low speed leveling feedback relay LRF in reducing the series resistance of the tachometer generator field 19 and increasing the shunt capacitance during low speed leveling results in a substantial increase in the output signal of the electrical output signal producing means 15 to in turn increase the current flow through the selected compensating field winding 33 or 34 to produce a low stable leveling speed. In adjusting the elevator con trol system constructed in accordance with the invention, the taps of the variable resistances 28 and 29, as well as the taps of the variable resistances R1 and R2 may be adjusted to provide a selected high leveling and low leveling speed resulting in a smooth, accurate stop with minimum floor to floor time.

Thus there has been provided, in accordance with the invention, a novel and improved feedback compensating system for controlling the accurate and smooth level-ing and stopping of an elevator car at a floor.

It will be understood by those skilled in the art that the above-described embodiment is meant to be merely exemplary and that it is susceptible of modification and variation Without departing from the spirit and scope of the invention. Therefore, the invention is not to be deemed to be limited except as defined in the depending claims.

I claim:

1. A control system for an elevator car adapted to travel between a plurality of floors, comprising a controllable electrical generating means for raising and lowering the elevator car at selectively variable speeds, selectively operable leveling and braking means for effecting a controlled stop at a selected floor as the car travels from one floor to another including selectively operable high speed leveling means and low speed leveling means for controlling said electrical generating means,

means responsive to the operation of said drive means for producing an electrical output signal representative of the speed of the elevator car, selectively energizable compensating means responsive to said electrical output signal and to the direction of travel of the elevator car for modifying the speed control of said electrical generating means, means responsive to the operation of said high speed leveling means for initiating the operation of said compensating means, means responsive to the operation of said low speed leveling means for varying the operation of said electrical output signal producing means to modify the operation of said compensating means, means for controlling the energization of said compensating means as a function of the direction of travel of the elevator car, and impedance matching means interposed between said electrical output signal producing means and said compensating means.

2. An elevator control system as claimed in claim 1, wherein said compensating means comprises a plurality of selectively energizable compensating field windings for said electrical generating means, said electrical output signal of said signal producing means having a polarity dependent upon the direction of travel of the elevator car, and respective polarity responsive electrical transducing means for each of said plurality of compensating windings.

3. A control system for an elevator car adapted to travel between a plurality of floors, comprising a con-- trollable electrical generating means for raising and lowering the elevator car at selectively variable speeds, selectively operable leveling and braking means for effecting a controlled stop at a selected floor as the car travels from one floor to another including selectively operable high speed leveling means and low speed leveling means for controlling said electrical generating means, means responsive to the operation of said drive means for producing an electrical output signal representative of the speed of the elevator car, selectively energizable compensating means responsive to said electrical output signal and to the direction of travel of the elevator car for modifying the speed control of said electrical generating means, means responsive to the operation of said high speed leveling means for initiating the operation of said compensating means, and means responsive to the operation of said low speed leveling means for varying the operation of said electrical output signal producing means to modify the operation of said compensating means.

References Cited by the Examiner UNITED STATES PATENTS 2,363,302 11/1944 Eames 187-29.21 2,414,562 1/ 1947 Santini 18729.21 2,643,741 6/1953 Esselman 18729 2,690,236 9/1954 Hancock et al. 18729 2,746,567 5/1956 Guttinger et al. 187-29 2,804,943 9/1957 Skiess 18729 2,821,672 1/1958 Sichling et al. 318-146 2,873,918 2/1959 Borden 318-162X 2,918,987 12/1959 Haase et al. 187-29 ORIS L. RADER, Primary Examiner. 

1. A CONTROL SYSTEM FOR AN ELEVATOR CAR ADAPTED TO TRAVEL BETWEEN A PLURALITY OF FLOORS, COMPRISING A CONTROLLABLE ELECTRICAL GENERATING MEANS FOR RAISING AND LOWERING THE ELEVATOR CAR AT SELECTIVELY VARIABLE SPEEDS, SELECTIVELY OPERABLE LEVELING AND BRAKING MEANS FOR EFFECTING A CONTROLLED STOP AT A SELECTED FLOOR AS THE CAR TRAVELS FROM ONE FLOOR TO ANOTHER INCLUDING SELECTIVELY OPERABLE HIGH SPEED LEVELING MEANS AND LOW SPEED LEVELING MEANS FOR CONTROLLING SAID ELECTRICAL GENERATING MEANS, MEANS RESPONSIVE TO THE OPERATION OF SAID DRIVE MEANS FOR PRODUCING AN ELECTRICAL OUTPUT SIGNAL REPRESENTATIVE OF THE SPEED OF THE ELEVATOR CAR, SELECTIVELY ENERGIZABLE COMPENSATING MEANS RESPONSIVE TO SAID ELECTRICAL OUTPUT SIGNAL AND TO THE DIRECTION OF TRAVEL OF THE ELEVATOR CAR FOR MODIFYING THE SPEED CONTROL OF SAID ELECTRICAL GENERATING MEANS, MEANS RESPONSIVE TO THE OPERATION OF SAID HIGH SPEED LEVELING MEANS FOR INITIATING THE OPERATION OF SAID COMPENSATING MEANS, MEANS RESPONSIVE TO THE OPERATION OF SAID LOW SPEED LEVELING MEANS FOR VARYING THE OPERATION OF SAID ELECTRICAL OUTPUT SIGNAL PRODUCING MEANS TO MODIFY THE OPERATION OF SAID COMPENSATING MEANS, MEANS FOR CONTROLLING THE ENERGIZATION OF SAID COMPENSATING MEANS AS A FUNCTION OF THE DIRECTION OF TRAVEL OF THE ELEVATOR CAR, AND IMPEDANCE MATCHING MEANS INTERPOSED BETWEEN SAID ELECTRICAL OUTPUT SIGNAL PRODUCING MEANS AND SAID COMPENSATING MEANS. 